Yes, 3. It was in the Open Beta FAQ.
How many characters can I create during this open beta? (Save Management)
In the context of this Open Beta, you will only be able to create one character with a dedicated saveslot.
If you experience any issue with your save or want to create a new Ghost, you can delete the existing save by using your PS4/Xone save manager or by deleting the file in Documents\My Games\Ghost Recon Wildlands\SAVES.
From March 7th, Tom Clancy’s Ghost Recon Wildlands will give you the opportunity to create up to 3 different characters with their own progression.